DOES MICROPLASTICS INDUCE SUFFERENCE IN XENOPUS LAEVIS EMBRYOS?

Microplastics (MPs), originating from industrial and household products or from the degradation of larger plastics, are nowadays pollutants of global concern. These particles are found in aquatic environments in high concentrations, up to thousands of particles per m3 , and may adversely affect aquatic organisms. The ability of MPs to adsorb pollutants and subsequently liberate them into marine and freshwater systems is an additional concern. Since Xenopus laevis embryos are a good model to study the effects of MPs accumulation, in this study, through FETAX assay, commercial polystyrene MPs of 1 and 3 µm were tested at 0.1, 1 and 10 mg/L concentration, to check for any adverse effect on embryonic development. The impact on heart rate, the influence on the expression of some early developmental genes and pro-inflammatory cytokines were investigated, together with ROS production. The localization and effects of MPs were analyzed with light and electron microscopy. Results indicate that microplastics cause a low mortality rate, reaching a maximum of 30% (3 µm at 10 mg/L). Embryos grow normally, except for those treated at 10 mg/L with 3 µm MPs, probably due to the ingestion of MPs which, as highlighted by microscopy investigation, would accumulate and cause significant harm to the intestinal epithelium. MPs induced a low malformation rate, even though very severe, and increased production of ROS ; moreover, levels of bmp4, fgf8, pax6 and rax1, master genes in embryonic development, were modified. Finally, the induction to an inflammatory state was supposed, considering the increased expression of tnfa and il1b. Our data indicate that the effects caused by MPs certainly depend on their size, but that concentration is the most important aspect to consider. Therefore, it is of fundamental importance to reduce the production of these substances and free the water from the already existing ones.